[Patch] mt_allocator: spare mem & fix alignment problems

[Dhruv Matani]

On Fri, 2004-03-26 at 17:52, Paolo Carlini wrote:
> Hi,
> 
> [snip]
> 
> Thanks for your interesting observations: in my opinion first we must figure
> out *exactly* where that 10x comes from...
> 
> >Another couple of issues that are pending would be:
> >
> >1. The use of the div instruction on every call of deallocate to
> >calculate the nodes to be removed. This is quite a high latency
> >instruction, but I don't know how much the performance is affected.
> >  
> >
> Probably not much, but I agree that we had better avoiding it, if 
> possible. I'll
> give it a try in a forthcoming batch of minor cleanups.

You could try this divide by 10 algorithm. It would give even mul a run
for it's money.

template <typename Int>
inline Int divide_by_10(register Int Num)
{
  register Int temp = Num;
  Num <<= 1;
  Num += temp;
  Num += temp >> 2;
  Num >>= 5;
  return Num;
}

Or for more accuracy:

template <typename Int>
inline Int divide_by_10(register Int Num)
{
        Num -= Num >> 2;
        Num += Num >> 4;
        Num += Num >> 8;
        Num >>= 3;
	return Num;
}

> 
> >2. The algorithm for giving back nodes to the global pool. Instead of
> >clipping out one node at a time, why not splice out a whole bunch of
> >nodes, and put them all in at one shot? Just a thought. I can prepare a
> >patch for this one if needed.
> >  
> >
> Looks like a nice idea. Please put together a patch for public scrutiny.

It's attached.

Just wondering, why aren't we incrementing the used count for the global
pool while adding blocks to it?




-- 
	-Dhruv Matani.
http://www.geocities.com/dhruvbird/

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